Texas oil millionaire Stanley Marsh 3, known for the "Cadillac Ranch," was indicted Thursday on more than a dozen counts related to child sex abuse.

Marsh, 75, faces up to 20 years in prison on each of the counts if convicted on the charges that include sexual assault, indecency with a child and sexual performance by a child.

Marsh, who considers the Roman numerals "III" to be pretentious and prefers the suffix "3," is best known as the owner of the iconic Cadillac Ranch, a work of public art that features 10 brightly painted Cadillac cars buried nose-first in the ground along Interstate 40 in the Texas Panhandle.

The indictment charges Marsh with offenses involving six victims, Lubbock County District Attorney Matt Powell said.

The allegations first surfaced in a civil lawsuit filed by two boys who were 15 and 16 years old when the incidents allegedly happened in 2010.

"The indictments filed today are mere allegations," Marsh's Houston attorneys, Paul Nugent and Heather Peterson, said in a statement. "Now that we have notice of the specific allegations, we will commence our investigation, which will be thorough and vigorous."

The incidents allegedly occurred in Amarillo, about 120 miles north of Lubbock. The district attorney for Potter County, which forms part of the Amarillo area, recused himself from the case and Powell made the presentation to the grand jury.

"We'll look at it to see if it needs to go to trial, or if we should make an offer in the case," Powell said.

Powell said Marsh's failing health would be one of the factors affecting his decision. Marsh suffered a stroke in 2011 and is said to be in poor health.

The iconic Cadillac Ranch, Marsh's most famous creation, has become a part of American culture as the subject of everything from a Bruce Springsteen song to an episode of the animated television show "King of the Hill."

Marsh has been no stranger to allegations of child sexual assault.

A separate lawsuit filed against March in 2012 claimed he paid 10 teenage boys to engage in sexual acts both at his office in Amarillo and at his home, called 'Toad Hall,' a reference to the Kenneth Grahame novel 'The Wind in the Willows.'

Other allegations of improper sexual activity with young boys date back to the mid 1990s. At one point Marsh served a 10-day jail term after pleading no contest to misdemeanor charges.